Electronically switched reluctance motor

ABSTRACT

This motor has a special magnetic circuit which enables it to be powered by a very simple electronic circuitry. This motor has, according to the figure, four U-shaped Yokes ( 11, 112 ) with eight unevenly spaced poles ( 111 ) surrounding a rotating six-pole rotor ( 12 ). The motor is driven by two power semiconductor devices ( 21 ) controlled from a Hall sensor ( 31 ). The demagnetising energy being set free by switching off the main windings ( 112 X) will be directed through the coupling diodes ( 22 ) as premagnetising energy to the secondary windings ( 113 Y) of the following phase (Y). This motor with high speed capability which is inexpensive, simple and quietly running can be mainly used for pumps, fans and blowers for gases and fluids.

The invention relates to a novel type of d.c. motor comprising woundmagnetic yokes, wherein the rotating field driving the motor is effectedby the electronic commutation of the windings of the magnetic yokes.

In contrast to the vast majority of electronically switched motor, themotor according to the invention requires no permanent magnets in orderto generate a useful torque and, for that reason, is more inexpensive tomanufacture than the normal motors of this type.

Such a motor is e.g. known from the prospectus of Messrs. TASC DRIVESLTD., United Kingdom. This motor possesses 8 stator poles and a six-polerotor revolving in the interior of the stator. The magnetic flux whichexcites the rotor, proceeds via two oppositely Located poles and passeshalf of the stator circumference as well as the diameter of the rotor;it thus passes in considerable Length non-wound iron yokes, which merelycause Losses.

The DOS 2953032/79, FIG.1, shows a motor type possessing three woundstator yokes which are insulated from each other. Since the stator yokesare Located so as to be disposed at 120°, thus not oppositely disposed,strong radial forces act upon the rotor which result in a premature wearof the bearings.

The technical problem of the invention is to show several possibilitiesof how to construct some types of electronically switched motors and tooffer generally applicable solutions both with regard to the magneticcircuit as well as regarding the commutation circuits with the object ofobtaining inexpensive, light-weight motors subject to low losses.

The solution of the technical problem is achieved by means of theteaching of the main claim, while the constructional details areillustrated in the independent claims or in the drawings.

Below some general theoretical considerations:

The electronically switched reluctance motors according to the inventionwere for a long time considered to be inferior to the motors which areexcited by means of permanent magnets because the magnetization energyof the poles does not come from permanent magnets, but every time theelectromagnetic poles are to attract the rotor poles, this energy has tobe supplied in an electrical manner. According to the teaching of theinvention, this energy is cyclically recovered and transferred to thefunctionally following yoke because the self-inductance voltage Ua,which comes from the demagnetization energy of a yoke 11Y, istransmitted in the form of premagnetization energy to the following yoke11X. On account of this, a saving in energy (a high degree ofeffectiveness) as well as a faster rise in the magnetic flux in theseyokes is achieved which are approached by rotor poles moving away fromthe poles which have just been switched off.

In order to provide a better understanding of the invention, a numberingsystem of the reference numbers of the drawings is defined here, whereinthe initial figures of the reference number indicates the subgroup towhich the designated object belongs: this is done as detailed in thefollowing:

The parts of the electromotive circuit (which produces the usefultorque) begin with the FIG. 1;

The parts of the electrical control circuit of the motor windings beginwith the FIG. 2;

The parts of the circuit which serve to detect the position of the rotorpoles relative to the poles of the electromagnetic excitation circuit,begin with the figure 3;

The parts of the magnetic circuit which the rotor moves into a startingposition (not available in all variants), begin with the FIG. 4.

The logic output from the Hall sensor is shown in FIGS. 5a and 5 b.

The motor control circuits are shown in FIGS. 6a-6 e.

The voltage between the control transistors and the windings is shown inFIG. 7.

The motor and pump assembly is shown in FIG. 8.

A variation of the motor is shown in FIG. 9.

The motor and fan assembly is shown in FIG. 10.

In principle, all these compoent parts are known in many variants fromthe state of the art and constitute the subject matter of the inventiononly to the extent in in which, by useful combinations, they interactwith the magnetomotive circuit (iron yokes and windings), whichpossesses important novelty features. The driving magnetic circuit ischaracterized in that, on the side of the wound magnetic yokes (and asfar as possible on the side of the rotor), magnetic paths (understood inthe form of lines of force of the magnetic force) are employed, whichare as short as possible. At least 50% of the length of the magneticcircuit of the wound yokes are located within the windings passedthrough by current, thus positively contributing to the development ofthe driving magnetic flux. In the most favourable case it may happenthat the windings comprise up to 90% of the length of the yokes 11. Thewound yoke (or yokes) is (are) disposed symmetrically opposite the rotorso that no radial magnetic forces are generated, but torques.

The FIG. 1 shows an overall view of a motor according to the inventionas a non-restrictive embodiment example. The magnetic motor circuit iscomprised of two horizontal U-shaped magnetic yokes 11X and two verticalmagnetic yokes 11Y, in which case the four yokes are identical. Eachyoke possesses two poles 111 esch, which are directed to the rotor andwhich assume the north or the south polarity when a current passesthrough the main windings 112 or through the secondary windings 113.

Consequently, there are eight poles constituting the segments of acircumference of a circle, surrounded by which the rotor revolvesaxially. The same has six poles 121, which are separated by a narrow airgap from the external poles 111, which possess an area correspondingapproximately to the area of the poles 111 and a width, whichcorresponds approximately to the opening of the two legs of the yokes11.

As can be gathered from FIG. 1, when four rotor poles 121 are locatedopposite four poles 111 of the vertical yokes 111Y, then the remaininghorizontal external poles 111X are located opposite the pole gaps 122 ofthe poles 121. The rotor poles 121 are interconnected by means of acommon rotor yoke 123 so that these parts are merely formations of thelamination pack of the rotor 12, which is comprised of punched-outelectromagnetic sheet metal possessing a round configuration withindentations. These parts are mounted with the aid of an elastic member53 on the motor shaft 52. This member is e.g. fabricated from a plasticpossessing elastic qualities and its purpose is to attenuate the rotorvibrations or to reduce its weight. This member 53 may be dispensed within case the bore of the rotor laminations 12 presses direct on the motorshaft 52.

The wound yokes 11 are likewise formed of U-configured sheet metallaminations, the thickness of the laminations being selected accordingto the rotational motor speed (commutation frequency). The standardvalue both for the thickness of the laminations of the yoke 11 as wellas for the thickness of the rotor laminations ranges from 0.1 mm to 1mm, in which case the thin lamellae are suitable for high rotationalspeeds (50,000 rpm) and the thick lamellae are employed for rotationslspeeds of up to approximately 500-1000 rpm.

As the most inexpensive material for the wound yokes 11 and for therotor 12, silicon laminations (for transformers) are recommended. Forthe wound yokes 11 it is also possible to make use of grain-orientedlaminations possessing a preferred direction in the form of U-shapedpunched lamellae (the preferred direction is in this case parallel tothe U-configured legs) or in the form of wound, cut and ground cores (asin the case of transformers with strip-wound cut areas). However, thesolution is a more expensive one. At any rate, the cross section of theyokes is rectangular, which may result in problems by winding withthicker wires (above 1 mm² cross section.

In a special embodiment, the insulating layer between the lamellaepossesses elastic properties which may serve to attenuate themagnetostrictive vibrations or for the sealing of the laminationpackage. Onto the U-shaped yokes (preferably prefabricated), windingsare slidably mounted, in which case, however, each yoke possesses atleast one main winding. These windings can be executed in a normalmanner with enamel-insulated wire, without a former (with self-bondingwire), see FIG. 2. In a normal wire winding, the secondary winding 113executed with thinner wire may be located on a former 114 underneath themain winding 112. However, according to the invention, a tape winding isemployed, to be more precise, of an insulated or non-insulated copper oraluminum tape. In the latter case, the main winding tape is flanked oneach side with an insulating foil 115 (e.g. of ployester), which issomewhat wider than the electrically conductive tape so that shortcircuits between the spirally wound edges of the metallic winding tapecannot take place, see FIG. 3.

A particularly favourable solution is the simultaneous execution of themain winding 112 and of the secondary winding 113 possessing a smallercross section. In this case the winding tapes possess an identicalthickness, but a different width, are wound at an appropriate distanceparallel over the identical, sufficiently wide insulating foil 115.Since in the construction of these windings techniques are used whichare known from the fabrication of capacitors and transformers, we willnot describe any details relating to the construction of the connectionsand to the strengthening of a former-less coil. Two each of the windingsdescribed in connection with the FIGS. 2 and 3 are slidably insertedover the two legs of the yokes 111, where they can be connected asrequired. Thus the motive magnetic circuit 1 is comprised of the woundyokes 11 with two cores 11X and 11Y each, eight main windings 112 and,possibly, eight secondary windings 113, together with the rotor 12.

When separately regarding one yoke 11 and two rotor poles 121, togetherwith that portion of the yoke 123, which connects these poles and whenthe two windings 112 are passed through by currents, a magnetic flux isproduced which corresponds to the dotted line in FIG. 1, so that thismagnetic circuit resembles the magnetic circuit of an oscillating motorof an electric razor.

When the rotor poles 121 are not located opposite the poles 111X of theexternal yokes (see FIG. 1) and when the yokes 11X are stationary, as aconsequence of the passage of current, the poles 111X will attract therotor poles 12 through approximately 30°. In order to have thesediscrete 30° of movement become a continuous rotational motion, it isnecessary that the current conduction to the yokes wound in thedirection of the axes X and Y be effected in a corresponding sequence,which is coordinated by the rotor position detecting circuit 3 and, bythe electronic control circuit 2, is converted into control signals ofthe windings.

The rotor position detection circuit 3 that is to supply theswitching-off signal for the windings of the X axis or the Y axisfollowing a rotor revolution of 30° is, according to the FIG. 4,comprised of a multipolar magnetic disk 32, which possesses six pairs ofpoles and is mounted on the rotor which is travelling in front of astationary Hall sensor 31, which, for the purpose of finding an optimalworking point, is adaptable in its position to the power control or tothe change of rotation. When the poles of the magnetic disk 32 moveconsecutively in front of the Hall sensor 31 (with digital output), thena logical signal “low” or “high” appears at the output of the latter,depending upon the rotor position, see FIG. 5.

The control circuit 2 of the windings 112 and 113 is mainly comprised oftwo power transistors (by preference MOSFET field effect transistors)21X,21Y, which are connected in series with the main windings 112X or112Y and the current source located externally of the motor, see FIG. 6.The windings 112 or 113X (or Y), which are to be found in oppositelylocated yokes, may be connected in series or in parallel, depending uponthe voltage level at which the motor is operating.

The transistors 21X and 21Y are controlled in the push-pull mode bymeans of a simple electronic circuit of the rotor position detectingcircuit 3 so that, when the output of the Hall senspr is on “high”, thetransistor 21X is conductive, while the transistor 21Y is conductivewhen the output of the Hall sensor 31 indicates “low”. The horizontallywound yoke 11X or the vertical yokes 11Y are also magnetizedconsecutively so that a rotary field appears at the poles 111 which setsthe rotor in motion.

The positive voltage at the junction between the drain of thetransistors 21X,21Y and the windings 112X and 112Y (as compared with0=minus) is depicted in FIG. 7 by means of a continuous line. Thecurrent, which passes through the main windings 112 possesses, onaccount of the effect of the inductivity, the course of the dotted lineof FIG. 7. Consequently, in the initial phase, the current rises slowlyand in a similar fashion also the effective driving magnetic flux. Whenthe winding is disconnected, a substantial voltage Ua is produced withinthe same, which higher than Un=motor nominal voltage, which constitutesa lost energy and can lead to a destruction of the transistors 21. Thisself-induction voltage Ua can be converted into a useful motive effectif it is supplied to the winding that is about to be switched on.

As becomes apparent from FIG. 6a, this has to be done with the aid ofthe coupling diodes 22, which supply a positive overvoltage, which isgenerated when the winding 112X is switched off, to the winding 112Y (orvice versa). The decoupling diodes 23 prevent the self-induction voltageUa from being supplied to the plus connection of the voltage source.However, this circuit is subject to the disadvantage that the closing ofthe electric circuit of the self-induction voltage Ua is effected by thetransistors 21 or via the current source. It is possible to avoid thisdisadvantage by the employment of secondary windings which are locatedon the same yokes 11, see FIG. 6b. The self-induction voltage Uadeveloped in the main winding 112X (as source) and is supplied to thesecondary windings 113Y of the vertical yokes as receiver. Consequently,with the aid of the self-induction overvoltage Ua from there mainwinding 112X, a useful current is produced in the secondary windings113Y, thus a magnetic flux in the yokes 11Y, upon which the same arewound. Simultaneously with the production of the current by thesecondary winding 113Y, also the nominal voltage UN is supplied to themain winding 112Y because, simultaneously with the blocking of thetransistor 21X, the transistor 21Y becomes conductive. The effect of therapidly rising transient current in the secondary winding 113Y, whichrises fairly fast and ths effect of the longer-lasting, but more slowlyrising current through the main windings 112Y are added, which resultsin a faster increase of the magnetic flux through the vertical yokes,thus in an increase in the driving effect. The rotor 12 is, by means ofthe repetition of the above-described actions, set in a continuousrotational motion so that the same executes a complete revolution wheneach pair of yokes receives six control pulses. The optimization of theswitching point can be practically effected by the displacement of theHall sensor 31 relative to the yokes 11.

The magnetic and electric components of the motor can be secured in anaccommodation frame 5 which is fabricated from plastic material ordiecast from a suitable nonmagnetic metal, see FIGS. 1 and 8. This framecan be executed in widely differing models, however, it possesses mainlyrecesses wherein the yokes 11 and the bearing 54 of the motor shaft aremounted.

On this frame 5, which serves as a cooler, it is possible to likewiseattach as per usual the power transistors 21, the diodes 22 and 23 aswell as other mechanical and elecrtical components (baseplate, Hallsensor, etc.). The higher voltage which is required for the gatetriggering of the power transistors 21, can be gained by the integrationof the peaks of the self-induction voltage Ua.

In order to provide a better understanding we will commence with theFIG. 1a, which is an enlarged detail of the FIG. 1. The FIGS. 1 and 1aare to be regarded in connection with the FIG. 6c, which is animprovement and detail of the FIG. 6b.

According to the FIG. 1, when four rotor poles coincide approximatelywith the poles 111Y, their associated main windings 112Y aredisconnected, which leads immediately to the appearance of the highself-induction voltage Ua, which is transmitted to the secondarywindings 113X, while the main windings 112X are supplied from thecurrent source. The four poles 111X allocated to these windings aremagnetized rather rapidly and are thereby capable of attracting the fourrotor poles 121 which are just moving away from the two relevant polesof the switched-off yokes 11Y. The precondition for this to take placeis that the acutely angled extermities of the poles 111X are located inthe proximity of the corresponding extremities of the poles 111Y sinceotherwise the magnetization of the poles 111X of the horizontal yokes isincapable of exercising an attraction effect on the rotor poles in goodtime so that the current in the windings 112X,113X would rise steeply,but without any useful effect.

In order to illustrate the importance of these facts, in the FIG. 1a,the distance regarded as angle “u” between the external corners of thepoles 111X and 111Y was reduced in comparison with the one depicted inthe FIG. 1. This distance has to be optimized depending on theelectromechanical parameters of the respective motors and it is at least3 to 4 times larger than the air gap between the yokes 11 and the rotor12 in order to avoid the occurrence of magnetic losses due to the directcontact between the yokes 11X and 11Y, The reciprocal attachment of theyokes 11 as well as the connection of the motor to a fixed support ispreferably effected within this area between the windings and the rotor,where a low level of vibration was noted.

The FIG. 6c illustrates the complete circuit diagram of an operativemotor, in which the dots next to the windings 112 and 113 designatetheir beginnings and 112X illustrates e.g. the four main windings of theyokes 11X that can be connected in series or in parallel.

Here, merely two coupling diodes 22 are required which conduct theself-induction voltage Ua further to the beginnings of the secondarywindings 113. The diodes 24 conduct the voltage peaks Ua to thecapacitor 25 which, subsequent to the starting of the motor, is chargedwith a voltage which is higher than the supply voltage U-bat and whichensure the supply of the control circuit of the gate electrodes of thetransistors 21Y,21X. This voltage is restricted by the Zener diode 26.When the switch 27 is closed, the Hall sensor 31 is energized and, atthe digital output of the latter which is connected to the gateelectrode of the transistors 21Y, the logical signal “high” or “low”appears, depending on whether a north pole or south pole of themultipolar magnetic disk 32 is to be found in front of the Hall sensor31. This logical signal is also applied to the signal inversiontransistor 28, which applies the “low” signal to the gate electrode ofthe transistor 21X when the signal “high” is apparent at the gateelectrode of the transistor 21Y. The arrow above the Hall sensor 31indicates that the same is movable in relation to its support so that itis possible to thereby alter the phase of the logical signals beinggenerated when the multipolar magnetic disk 32 is rotated. The controlof the rotational speed of the motor can also be effected withoutchanging the phase of the control signals by means of a change in thesupply voltage. It is also possible to effect the change in therotational speed by changing the resistance of the transistors 21, thusby controlling the gate voltage. However, this control isdisadvantageous because it causes ohmic losses, strains the transistorsand should therefore be used solely for low outputs. A two-step controlmay be effected by increasing the ohmic resistance of the motor, e.g. bythe separation of one half of the parallelly connected windings, seeFIG. 6d. The windings 112,112′ connected in parallel via the transistors21,21′ are simultaneously controlled when the full output is demanded ofthe motor. If an output reduction is desired, in that case thetransistors 21′ are no longer triggered and the winding 112′ remainsinoperative. Hence the motor operates with higher lossess and with areduced output. A more advantageous variant of the more extensive outputcontrol is shown in principle following FIG. 6c.

Two further semiconductor modules (here bipolar transistors) are addedto the control circuit of the motor which play the part of afree-wheeling diode, which return the self-induction voltage of thewinding which has generated the same, but which are controllable thistime. The FIG. 5b shows, independently of the rotor angle of rotation,the control signals of the transistors 21 and the transistors 211, whichreturn the self-induction voltage Ua. On the abscissa of FIG. 5b, theoutput signal of the Hall sensor is illustrated, which corresponds to arotor angle of 30° and which has the same duration as the current pulsewhich is applied to the base of the transistors 211Y. The duration ofthe positive voltage pulses being applied to the MOFSET transistors 21Yfor the output control is illustrated in two variants on the lowerabscissa, where this duration reaches 30° only at full load. In thefirst variant A, the transistors 21 and 211 become conductivesimultaneously and this when the logical signal at the output of theHall sensor changes from “low” to “high”. At partial load the transistor21Y blocks before the Hall sensor switches once more to the logicalsignal “low”, thus before the rotor performs a 300 rotation. Theblocking of the transistor 21 can e.g. be brought about by reaching alimit value of the current or of the rotational speed (the commutationfrequency). When this happens, the self-induction voltage Ua is notsupplied immediately to the secondary winding 113X because thetransistor 211Y conducts this voltage to the plus connection of thesupply voltage U-bat. The demagnetization of the yokes 11Y, whichcontinues to attract the rotor poles 121 is curbed thereby. When therotor angle of rotation of 30° is reached, i.e. when the base current ofthe transistors 211Y stops and the output of the Hall sensor 31 assumesthe logical level “low”, the passage of the residual current through thetransistor 211Y ceases and the self-induction voltage Ua is supplied tothe secondary winding 113X. In a similar manner, but with a rotor angleoffset through 30° (e.g. 30-60° instead of 0-30°), what happened withthe Y axis is repeated with regard to the horizontal yokes 11X, thetransistors 21X and 211X thus become conductive because the logicalsignal at the output of the Hall sensor became “low” instead of “high”.Consequently, by means of this type of control, the control of thetransistors 21X, 211X is achieved in a rotor angle-dependent manner witha variable angle reaching maximally 30°, thus not a fixed 30° apertureangle as in the uncontrolled motors.

By means of this variation of the opening time of the transistors 21,the energy supply, thus the motor output, is controlled. According tothe variant B depicted in the FIG. 5b, a similar effect is achieved bythe repeated current conduction of the transistors 21X,21Y within arotor angle of 30°. This is achieved by a pulse width modulation(L=pulse, l=interval) with an appropriate frequency of the controlsignals of the transistors 21. The current conduction times of thetransistor 21Y are illustrated with a boldly drawn line and those of thetransistor 21X with a dashed line. It is advantageous to integrate allelectronic component parts of the motor as far as possible on ay singlecircuit board. The mounting of the yokes 11 visible in the FIGS. 1 and 8is (on account of the narrow air gap between rotor and wound yoke)important and exacting. As becomes apparent here, the yokes 11 possesson both sides (if possible, at two different distances from the shaft)recesses or semicircular elevated portions 116 which, by means ofsuitable counterpieces 55, can be matchingly (vertically to the plane ofthe drawing) inserted. These counterpieces constitute a negative form ofthe recesses 116 mentioned in the foregoing and are an integral part ofthe attachment pieces 56 which are to be found mounted on a baseplate57.

The yokes are therefore attached positively and radially, which ensuresa uniform distance relative to the rotor 12 (a constant air gap). Thebearing cover 58 with the counter-bearing 54′, which are attached bothaxially as well as radially to the frame 5, retain the yokes 11 inposition so that the same are incapable of being axially displaced.—Withthese component parts the motor is operative.

Mode of Operation

When the motor is connected to a current source possessing the voltageUn, then the electronic circuit 2 will apply a control voltage to thegate electrode of one of the transistors 21, e.g. to 21Y, because asignal level “high” or “low” will exist at the output of the Hall sensor31. The main winding 112Y is energized and moves the rotor 12 from theinitial position illustrated in the FIG. 1 through a rotation of 30° toa position in which the poles 111X-121 coincide. Consequently, from therelative position of the poles in relation to the Y axis it comes to asimilar position, but this in relation to the X axis. Before thisposition is reached, the rotor position detector 3 changes the logicallevel at the output of the Hall sensor 31 so that the transistor 21Xbecomes conductive, whereas the transistor 21Y blocks. The operationsalready described are repeated and the rotor revolves continuously andexecutes a full revolution relative to the wound yokes 11 after each ofthese pairs (X and Y) has received six current pulses. The stopping orthe starting of the motor can be achieved in that the gate connectionsof the transistors 21 are connected to negative wire without separatingthe motor from the voltage source. In a digital Hall sensor 31, thechange of the logical,output signal always takes place at the samerelative angle of the rotor poles 21 in relation to the poles 111 of theyokes 11, this position being designated as angle 0. It may be necessaryin the interest of the output or rotationsl speed control to change thisangle e.g. by +/−5°. This can be achieved by the mechanical change inthe position of the Hall sensor ot by influencing its switching pointwith the aid of an external magnetic field, which alters the changingmagnetic field of the multipolar disk 32 (by means of a phase shift).

If an analog Hall sensor is employed, in that case a sinusoidal signalis generated at the output of the latter in lieu of the square-wavesignal as per FIG. 5. The change-over point can in this case be changedrandomly relative to zero when any point whatever of the curve of sinesis selected as switching voltage level for triggering the commutation.

As mentioned in the foregoing, also this curve of sines can bephase-shifted so that in this case two possibilities exist forinfluencing the angle of commutation. The influencing of the magneticfield mentioned can be practically achieved with the aid of a winding orof a permanent magnet, which are fitted within the proximity of the Hallsensor, in which case a current passes through the winding which isalmost constant. The change in rotation can be brought about by changingthe logical signal of FIG. 5 so that the transistor 21X becomesconductive when the logical signal of the Hall sensor is “high” insteadof “low”, or by the changing over to another Hall sensor which, incomparison with the former, is angularly displaced.

The brushless motor variants illustrated here are capable of operatingimmersed in a liquid, e.g. a fuel, if the elactrical parts areprotected, by way of example, embedded in a synthetic resin. It is alsopossible to realize with these motors simple pumps devoid of any air gapsealing, in which case the entire motor is accommodated in a pressurizedpump housing. This type of motor is particularly suitable for drivingfans and pumps, more especially for those wherein the rotor of the motoras well as that of the pump rotate in solidarity with a liquid, see FIG.8. In this case it is necessary for the rotor chamber to be sealedrelative to the windings or the outer space. The chief problem here isthe sealing of the cylindrical air gap space because the radial dimesionof the latter is in the order of magnitude of 0.1 mm.

This problem is resolved along the lines of the invention with the aidof a thin, cylindrical shell of nonmagnetic material (plastic or polymerapplied in the liquid state), or special special steel possessingspecial electrical and magnetic properties, are e.g. known from the airgap pipes of the wet-running asynchronous motor pumps. This cylindricalmember would not be able to withstand the pressure on its own; but it issupported upon the external poles 111 or upon segments of fillingmaterial 511, which are to be found between said poles. In this mannerthe pressure merely acts on areas of the cylindrical shell 512, whichare not larger than a few 0.1 mm and which correspond to the spacesbetween the poles 111 and the segments 511. When subjected to pressurein such small areas, even a thin foil (0.1 mm) is able to resistpressures of some tens of bars.

An assembly of motor and pump along the lines of the invention can, asper FIG. 8, be executed as detailed below.

The yokes 11 are mounted from the outside (from the left) on the frame 5(fabricated from plastic or metal) and fitted through the retaining ringor retaining cover 59. The previously mentioned interspaces of thecylindrical rotor chamber are sealed e.g. with a polymer varnish, anepoxy resin, etc. The rotor 12 with the multipolar magnetic disk 32secured to the left-hand side is, together with the pump rotor 62 whichengages lockingly into the rotor 12, mounted on the motor shaft; themotor shaft 12 must also not transmit the useful motor torque. Theassembly is closed with the pump cover 63, which also centers thebearing bolt 61′. The known constructional details of a pump are notdiscussed here, merely the direction of flow of the pumped liquid isindicated by means of arrows. The Hall sensor 31 is located in the (dry)outer space of the pump and is separated by a thin, pressure-proof andmagnetic field-pervious wall from the magnetic disk 32, which is locatedin the “wet” space.

The motor or pump shaft 52 is e.g. fabricated from a ceramic pipe, inwhich bores are provided for the bearing bolts 54′ and 61′. Thereduction of the noise generation is one of the main problems of theventilators and blowers and the noise is sometimes produced by virtue ofthe torque fluctuations that are transmitted to the support. In order toeliminate this disadvantage it is possible according to the invention torealize a special variant of a motor blower possessing two rotorsrevolving in opposite directions so that the motor possesses no fixedcomponents that are capable of transmitting vibrations to a supportwhich are to be put down to the torque. According to the FIG. 10, theyokes 11 with the windings 112,113, together with the associatedelectronic component parts, are mounted on a support 5, in which casethe support is also connected to a rotary shaft 52 which preferablypossesses an axial bore. Fan blades 64 are likewise fixed to thissupport, which convey the air from the right to the left when thesupport 5 rotates to the right. At the ends of the shaft 52, bearings541 or 542 are provided. on the left-hand side, the yokes are this timein comparison with the support 5, not mounted on a bearing cover, but ona retaining ring 59, through which the rotor 12 is passed. The rotor 12carries fan blades 641, which convey the air from the right to the leftwhen the rotor turns to the left. The rotor revolves freely on the shaft52 with the aid of the bearings 543 without becoming axially displaced.in the interior of the shaft 52, within an insulating tube, tworeciprocally insulated brishes 521+, 521− connected to motor leads 52are accommodated, which are urge outwardly by springs 522. These brushestouch two fixed leads +, −, which are connected to the current sourceUbat, which transmit this voltage on to the rotating brushes 521+, 521−.The bearings 541 and 542 are mounted in a support S.

Mode of Operation

When the motor receives current, both the rotor 12 provided with fanblades 641 as well as the external rotor assembly with yoke 11, support5 and blades 64 start in opposite directions of rotation (the roror tothe left, the external rotor assembly to the right) and move atrotational speeds +v, −v so that the absolute rotational speed betweenrotor and external rotor assembly is 2 v. The rotational speed of thetwo counterrotating parts will increase until the resistance with whichthe ait opposes the blades 64,641 which are mounted on the two rotors isexactly as great as the motor torque. This blower with the twocounterrotating rotors has the advantage of acting in the form of atwo-step blower with a relatively low rotational speed, thus with a lownoise level. However, for the motor, the design rotational speed (therelative rotational speed) between the two counterrotating parts) willbe 2 v. In comparison with a conventional single-stage blower with thesame output the advantages are manifest:

No reaction torques, thus no rotational vibrations, are transmitted tothe support S;

the motor is designed for a double rotational speed with the same outputand becomes significantly smaller and lighter thereby.

With the aid of this principle it is possible to construct, in lieu ofan axial blower, counterrotating blowers with radial fans so that theaxial forces are compensated in this case. If one strives for the outputcontrol with these motors, in that case it will be necessary to act fromthe outside on the transistors 21 rotating together with the externalrotor assembly 11, 5. This is possible by means of suitable electronicsknown from the state of the art which, from the outside, devoid of agalvanic connection, e.g. in a magnetic fashion, with the aid of atransmitting winding and a receiver, or in an optical manner, receivescontrol signals. Thiy type of motor (or type of pump) with the simpleoperating principle that is based upon the successive attraction of therotor poles by electromagnetic poles, can also be executed with adiffering number of yokes, e.g. six or eight instead of four, with thecorresponding increase in the number of the rotor poles. It can also beexecuted in a polyphase manner, e.g. with three phases R, S, T, whichare equidistantly disposed, thus at an electrical angle of 120° in lieuof 180° as hitherto.

When the rotor poles or the electromagnetic poles are expedientlyadapted, it is also possible to employ “U”-type yokes, whose legs arearranged axially instead of tengentially. In this motor it is alsopossible to dispense with the rotor position detecting sensor; this doeshowever mean that one has to employ a somewhat complicated electronicstarting and operating program, in accordance with the followingprinciple:

Prior to the starting of the motor, electric signals are supplied intothe windings which are changed independently of the winding inductivity,in which case the former depends upon the rotor position because thesame causes the reluctance (inductivity) of the magnetic circuits of theaffected yokes.

An electronic logic compares these modified signals and determines therotor position therefrom so that, at the output of this circuit, acontrol signal of the transistor 21X or 21Y appears.

The windings which are disposed in series with the conductivetransistor, are triggered and set the rotor in motion, which ismagnetized by influence.

When the thusly magnetized rotor poles approach the de-energized poles,a voltage is induced into the same which is evaluated by a circuit whichsupplies the nominal voltage to this winding (phase) so that the rotorcontinues to be attracted. These operations are repeated so that therotor revolves as if it were controlled by a rotor position detectionsensor.

Once the starting of the motor has taken place, also other automaticcontrol possibilities exist for the commutation, such as e.g. thedisconnection of a winding when the current passing through the sameexceeds a maximal or predetermined value; when such a value is reachedin the course of the normal motor operation, this means that the rotorpoles 121 have already been attracted by the poles 111, which form partof this winding.

The disconnection of a winding (e.g. 112X) results, via the electroniclogic, in the switching on (possibly after a predetermined delay) of thefollowing winding, e.g. 112Y. The interlinked cyclic control of the yokepairs X-Y, Y-X, or R-S-T, R-S-T . . . if three (or more) phases exist,can also be controlled by means of rotor position detecting sensors or,in dependence of a motor parameter (current, induced voltage). Thiscyclic control can in some cases be enforced from the outside, in whichcase the motor operates at a rotational speed predetermined from theoutside. In this case the transistors 21X,21Y are controlled by signalswhich come from a generator external to the motor. For this type ofcontrol the use of an asynchronous rotor (squirrel-cage rotor) in lieuof the rotor described in FIG. 1 can be of advantage. When bearing inmind the same electromagnetic criteria, this type of motor can also beexecuted with yokes which are located in the interior of a cup-shapedrotor.

A simpler variant of a motor along the lines of the invention isillustrated in FIG. 9. This motor possesses only two oppositely located,wound yokes 11 and a single power transistor 21, which is disposed inseries with the windings of these yokes and merely four rotor poles 121.The electric circuit corresponds to FIG. 6a, however without possessingthe component parts of the axis “X” (yokes 11X, winding 112X, transistor21X). The diodes 22 and 23 arew not necessary. The rotor of this motorpossesses two or four rotor positioning magnets 4, which move the sameinto the starting position, which corresponds to the current conductionphase of the transistor 21 or to the rotor position in which the rotorpoles 121 do not coincide with the poles 111 of the yokes 11. Thesemagnets can, for the purpose of detecting the rotor position, alsotrigger the Hall sensor 31 and possess small dimensions and, for thatreason, exert forces which, in comparison with the electromagnetic forceacting upon the rotor 12, are insignificant.

Mode of Operation

Since the positioning magnets 4 are attracted underneath the poles ofthe yokes 11, the rotor assumes the position mentioned in the precedingparagraph. The transistor 21 becomes conductive, the poles 111 of theyokes 11 are magnetized and attract the rotor poles 121 located closest.When the rotor poles 121 almost coincide with the external poles 111,one of the magnets 4 will move past in front of the Hall sensor 31 andchange the logical state of the same, so that the windings becomede-energized. The rotor continues to move under the influence of inertiauntil it comes to a relative position of the rotor poles 121 in relationto the poles of the yokes 11, which corresponds to the initial position.On the way to this position, another magnet 4 will move past in front ofthe Hall sensor 31 and change the logical state of the same so that thedescribed operations are repeated and the motor operates. If matters aresimplified further, in that case a motor can be constructed similar tothe one depicted in FIG. 9, but which possesses only one wound U-typeyoke which, between the extended U-type legs, comprises circularsegments which act as poles 111, between which a rotor 121 possessingbut two poles is revolving, while the latter is intermittently actuatedtwice per rotor revolution with useful torque angles of approximately90°, which correspond to two current pulses. Especially with motors forhigher voltage levels it is possible to employ, instead of the MOFSETtransistors 21, also other semiconductors such as thyristors (possiblythose which can be disconnected above the gate, thus GTO), bipolartransistors, etc., while adapting the electronic control circuit 2 as isknown from the state of the art.

What is claimed is:
 1. Electronically switched reluctance motor withwound yokes (11) magnetically separated from each other for thegeneration of a pulsating magnetic field and with a rotor (12) that isrotatable in relation to the yokes (11) with the rotor poles (121) whichare attractable by the poles (111) of the yokes, in which case thisatraction in dependence of the position of the rotor poles (121)relative to the poles (111) of the wound yokes (11) is electronicallycontrollable, while at least one winding (112) of a yoke (11) isswitchable by means of a power semiconductor (21) in series with a d.c.voltage source and the power conductor (21) is controllable independence of the position of the rotor poles (121) relative to thepoles (111) of the yokes (11), the poles (111) of the wound yokes (11)as well as those of the rotor (121) are disposed in pairs anddiametrically symmetrical relative to the rotating shaft (52) of themotor and wherein, between the rotor poles (121) of the rotor (12),non-magnetic gaps (122) exist and the rotor poles (121) are connected bya yoke (123), characterized in that the yokes (11) are U-shaped and thenumber of U-shaped yokes (11) is four, the yokes (11) carry windings(112), which, on a circular circumference, form eight magnetic poles(111), the number of the rotor poles (121) of the rotor (12) is six andthe distance between the external corners of the poles (111X,111Y) ofadjacent yokes within the region of the air gap is smaller than thedistance between the internal corners of the two poles of a yoke (11)within the region of the air gap.
 2. Motor according to claim 1,characterized in that it is an electronically commutated two phase (X,Y) motor.
 3. Motor according to claim 1, characterized in that thedistance between the external corners of the poles (111X, 111Y) ofadjacent yokes (11) within the region of the air gap is selected to besmall that it is optimized with regard to the magnetic losses, while thedistance is at least three times as large as the air gap.
 4. Motoraccording to claim 1, characterized in that the yokes (11X, 11Y), withinthe region between the windings (112) and the rotor (12) arereciprocally attached so as to be disposed in a radial arrangement. 5.Motor according to claim 1, characterized in that the yokes (11) areprovided with recessed or elevated points (116) which engage intocorresponding recessed or raised points in counterparts (55) disposedbetween the windings (112) and the rotor (12) for the positiveattachment of the yokes (111).
 6. Motor according to claim 5,characterized in that the counterparts (55) form component parts ofmounting pieces (56) which are secured to a baseplate (57) of a rigid,non-magnetic frame (5), and in that the magnetically acting parts(11,12) of the frame are positioned relative to each other with the aidof the frame (5).
 7. Motor according to claim 1, characterized in thatit possesses windings (112, 113) which are fabricated from at least onespirally wound metallic tape, while the windings are insulated from oneanother by an insulating sheeting or by means of an insulating layerapplied to the tape.
 8. Motor according to claim 7, characterized inthat the same possesses at least one main winding (112) with a secondarywinding (113), said windings being comprised of metallic tapes and arewound at a distance next to each other and parallel to each other. 9.Motor according to claim 1, characterized in that the same possesses amultipolar magnetic disk (32) secured to the rotor (12) and only oneHall sensor (31) having a digital or analog output, in front of whichthe magnetic disk (32) is rotatable relative to the motor windings forcontrolling the current supply.
 10. Motor according to claim 1,characterized in that a digital output of a rotor position detectingsensor (31) triggers direct the gate electrode of a power semiconductor(21Y) for selecting a winding and triggers indirect, by means of aswitching semiconductor (28) supplying the complementary logical state,another power semiconductor (21Y) for another winding.
 11. Motoraccording to claim 1, characterized in that the power or speed controlcan be effected with the aid of a phase shift of the triggering signalsfrom power semiconductors (21) for triggering the windings (112),whereas the phase shift can be effected with the aid of a localdisplacement of the position of a hall sensor (31) or by means of theaction of a magnetic field.
 12. Motor according to claim 1,characterized in that the direction of rotation of the motor can beeffected with the aid of the inversion of the logical signal of a Hallsensor (31) or with the aid of the changing over between two Hallsensors (31), that are disposed in different angular positions relativeto the yokes (11).
 13. Motor according to claim 1, characterized inthat, with the aid of logical comparison processes of the inductivity ofthe magnetic circuits (1) relative to the rotor (2), the rotor positionis detectable and in that this electronic information can be utilizedfor controlling the running or the starting of the motor for thesuccessive triggering of power semiconductors (21) for the triggering ofthe windings (112).
 14. Motor according to claim 1, characterized inthat the control fo the semiconductors (21) for the triggering of thewindings (112) takes place with the aid of an electronic circuit havinga fixed program not comprising the detection of the rotor position. 15.Motor according to claim 1, characterized in that the same possesses arotor with a squirrel cage winding.
 16. Motor according to claim 1,characterized in that the same possesses a rotor chamber which is sealedto the outside with the aid of a thin shell (512) comprised of plastic,of a polymer or elastomer layer or of a metallic alloy possessingsuitable magnetic or electrical properties, in which the shell is actedupon by compressive forces merely in small intermediate areas and, withthe largest part of its surface area, is supported upon the externalpoles (111) or upon a non-magnetic filling disposed between the externalpoles (111).
 17. Motor according to claim 1, characterized in that therotor (12) of the motor is positively connected to the pump rotor (62)of a motor-driven pump, in which the rotor (12) of the motor and thepump rotor (62) are mounted on a shaft (52), preferably comprised ofceramic material, which is rotatable between bearings (54) so that theshaft (52) does not transmit any torque stress of the pump rotor to therotor (12) of the motor.
 18. Motor according to any of the precedingclaims, characterized in that the same possesses lamellae that aresecured to one another by means of an insulating adhesive agentpossessing elastic properties.
 19. Electronically commutated D.C. motorwith at least two magnetically separated yokes (11) carrying windings(112) which are angularly disposed relative to each other in thedirection of rotation of the motor, wherein the demagnetization energywhich is produced when the windings (112) are disconnected, isreciprocally transmissible by the yokes (11) with the aid of couplingdiodes (22), more particularly according to claim 1, characterized inthat the self-induction voltage (Ua), which comes from a winding (112),can be tapped at a joint between this winding and a power semiconductor(21) for triggering the winding (112) and, by means of a coupling diode(22), can be connected direct to the beginning of a winding (112)disposed on the functionally following yoke (11).
 20. Motor according toclaim 19, characterized in that, in each case, not more than one powersemiconductor (21) is connected in series with a winding (112). 21.Motor according to claim 19, characterized in that, the yokes (11), inaddition to the windings serving (113), and in that the self-inductionvoltage (Ua) coming from a main winding (112), can be tapped at a jointbetween this main winding and a power semiconductor (21) for triggeringthe main winding (112) and can be conducted through diodes (22) to thebeginning of a secondary winding (113) mounted upon a functionallyfollowing yoke (11).
 22. Motor according to the claim 21, characterizedin that the self-induction voltage (Ua) produced when a controlsemiconductor (21) is disconnected, during the period of time in which arotor position sensor (31) does not change its logical state, can bereturned with the aid of further, controllable semiconductors (211) tothe main winding (112) wherein it originated.
 23. Motor according to theclaim 22, characterized in that the power semiconductors (21,211) of aphase (X,Y) become simultaneously conductive, but the blocking of thefurther semiconductors (211) only takes place with the change in thelogical state at the output of the rotor position sensor (31).
 24. Motoraccording to the claim 1, characterized in that the peak of theself-induction voltage (Ua) can be stored in a capacitor (25) forgaining the control voltage of a power semiconductor (21). 25.Electronically commutated motor according to claim 1, characterized inthat the rotor (12) and the external rotor comprising wound yokes (11)with a support (S) and in that the rotor (12) and the external rotor arerotatable in the opposite direction for the generation of, in each case,a part of the utilizable motor output.
 26. Motor according to the claim25, characterized in that the support (S) possesses two bearings(541,542) for supporting a rotating shaft (52), while an external rotorsupport (5) for the external rotor (11) rotatable conjointly with therotary shaft (52) is mounted on the rotary shaft (52) and in that therotary shaft (52), on its extremities, possesses brushes (521+, 521−)for the transmission of the energy required by the motor.
 27. Motoraccording to the claim 26, characterized in that the rotor is providedwith fluidic displacement parts (641) and is insertable into theinterior of the external rotor (11) or of the external rotor support (5)and is rotatable by means of a bearing (543) in relation to the latter.28. Motor according to the claim 25, characterized in that both therotor (12) as well as the external rotor (11) drive fluidic displacementparts (64,641) of a counterrotating blower or of a counterrotating pump.29. Motor according to the claim 25, characterized in that the controlof the motor output can be effected by a stationary part devoid ofgalvanic contact, more particularly with the aid of optoelectric means,or by the action of magnetic fields upon the electronic rotating modulesof the motor.